Epoxy resin is widely used in many industries. Within the aerospace industry, such resins are categorised as being self-reactive products and their transportation is categorised as “Class 4”. By the term “self-reactive” is meant that the resin ages, degrades and/or sets when it is above a certain mass or volume. This means that only a limited quantity of material is allowed to be transported in a single drum which typically contains a maximum of 10 kg of the resin. Moreover, during transportation, the resin needs to be refrigerated to around −18° C. to reduce the risk of reaction and to ensure conservation of the resin. The transportation of such Class 4 products is expensive.
Some epoxy resin manufacturers have developed two-component epoxy resins to overcome the transportation issue. Each component of such two-component epoxy resins is not self-reactive alone and is therefore easier to transport in larger quantities, that is, greater than 10 kg.
However, for a same qualified resin transfer moulding (SQRTM) process, only a small quantity of resin is required to apply pressure to a part during the moulding process. SQRTM is a closed moulding process that combines pre-form processing and liquid moulding to produce an autoclave-quality part without the need for an autoclave that is suitable for use in aerospace parts. The pre-form has already been shaped and impregnated with resin prior to insertion into the mould. Once the mould is closed, only a small additional quantity of resin needs to be injected around the part in order to exert the hydrostatic pressure that is necessary to consolidate the pre-form in the mould and eliminate any gas bubbles that may form during the setting of the resin.
Epoxy resins can be coated as a film onto a backing sheet, for example, silicone-coated paper, and the epoxy-coated backing sheet is then rolled up onto a cylindrical former to form a roll. The presence of the backing sheet or paper reduces the self-reactivity of the roll and transportation of such a roll is not categorised as being Class 4. However, the roll still needs to be refrigerated to around −18° C. to reduce the risk of reaction and to ensure conservation of the resin. Typically, epoxy resins have a life of around 15 days at room temperature and a life of 6 months when stored at −18° C. For SQRTM, it is important that the resin is not close to the end of its life when it is to be injected so that it does not react prematurely, for example, setting in feed passages, resulting in a sub-standard part.
Having coated the resin as a film onto a backing sheet such as silicone-coated paper and rolled the backing sheet and resin film into a roll for transportation, the resin needs to be removed from the backing sheet so that it can be used. The resin can be removed from its backing sheet in many ways, but the effective life of the resin may be reduced. In U.S. Pat. No. 5,807,480, apparatus for peeling and removing a coated film on a resin product is described. A shearing device is used for shearing and removing protruding portions of the resin product from a coated film. A pair of rollers having different effective rotational speeds is used to create a shear stress between the coated film and resin product to effect removal of the resin product from the coated film.
In WO-A-2011/033309, resin residue removal from a backing sheet is described so that the backing sheet can be re-used. A non-contact heat source is directed towards the backing sheet so that any residual resin is heated to reduce its viscosity so that the residue can be removed from the backing sheet.
However, the process described in U.S. Pat. No. 5,807,480 is not efficient as resin residue may remain on the coated film and the resin degrades due to being substantially at room temperature. The process described in WO-A-2011/033309 degrades the residual resin as it requires the resin to be heated for removal from the backing sheet.